The present invention relates to the repair of automatic transmissions and in particular to a simple method using a low cost clip to repair an automatic transmission by limiting the movement of a Torque Converter Clutch (TCC) regulator apply valve in General Motors 4L60E, 4L65E, and 4L70E automatic transmissions.
TCCs are incorporated into automatic transmissions to lock a torque converter to provide better efficiency. During unlocked operation, for example, at startup, the torque convert provides torque multiplication and smooths impulses from the engine. Unfortunately, torque converters reduce overall power train efficiency by about ten percent. At higher speeds, the torque multiplication and smoothness is not required, and the TCC may be applied to directly couple the torque converter input from the engine to the automatic transmission, thereby eliminating the inefficiency otherwise experienced.
A TCC oil circuit controls flows and pressures of oil between the TCC valve and the torque converter. Known TCC operation is described as follows. When operating conditions for engaging the TCC are met, a Powertrain Control Module (PCM) energizes the TCC on-off solenoid. Energizing the TCC on-off solenoid causes the TCC on-off solenoid to close, shifting the TCC valve, thereby switching fluid connections in the TCC valve. Switching the fluid connections in the TCC valve results in pressure being released in the converter release circuit and converter release oil exhausting at the converter clutch valve down through check ball #9 on the end of the torque converter turbine shaft (sometimes called “input shaft”). Simultaneously, a regulator apply circuit is connected to a converter apply circuit pressure equal to the pressure in the regulator apply circuit. The oil pressure in the oil circuit is applied to a converter lockup apply piston in the torque converter to lock the TCC.
Pressure regulation in the regulator apply circuit is controlled as described in the following. An actuator feed limit valve regulates pressure in a pressure regulated circuit. The pressure regulated circuit is further regulated by a TCC Pulse Width Modulator (PWM) regulator solenoid. Pressure in the pressure regulator circuit pushes the isolator valve into the TCC regulator apply valve opening the TCC regulator apply valve to increase pressure to the desired oil pressure level.
Unfortunately, wear occurs in the TCC regulator apply valve 24 and isolator valve 25 body bores due to an oscillation inherent to the operation of the TCC PWM regulator solenoid acting on the TCC regulator and isolator valve. The wear results in a lower than required pressure in the converter apply circuit 20d. The TCC PWM regulator solenoid is unable to compensate for reduced pressure, and additional leaking resulting from the wear, which results in the TCC slipping too much. A code 1870 (trans component slipping) results. The TCC slip code is then stored in the transmission computer causing the malfunction indicator lamp to light up on the dashboard. The code and resulting check engine light or malfunction indicator light keeps the vehicle from being registered in most US states making repairs necessary. Generally, the automatic transmission is repaired by replacing the valve body at a cost of $300.00 dollars or more, by using fixtures to ream out and use oversize valves, or by a tedious and time consuming process of using different shims selected to fit the four or more different types of original equipment valves and other aftermarket valves. A less expensive method of repairing the common failure is needed.